The present invention relates to the field of handling calls for an automated attendant or a voice mail system that is shared by multiple users. More particularly, the invention relates to transferring information about the user to whom a call is directed from a switch that receives the call to the automated attendant or voice mail system.
Frequently several users or tenants will share a telephone switch (such as a private branch exchange, PBX, or key service unit, KSU) and a voice mail system in order to reduce expenses. The users and the tenants of the switch and voice mail may be in the same building or facility or may be in different locations. To share the switch, the users will normally purchase several telephone lines to connect the switch to the public telephone company""s Central Office, CO. This allows several external or outside telephone connections to be maintained by the switch at the same time. The telephone lines will have one or more external telephone numbers that are typically divided up between the users and grouped for the tenants for exclusive use by the users of each respective tenant. The assignments of the telephone numbers to each tenant and to each user is normally maintained as a table at the switch.
Incoming calls will be received by the switch and matched to a particular one of users and a particular one of the tenants based on the corresponding telephone number or telephone line. Based on this identification, the switch can route the call to a particular one or more telephone terminals, to a receptionist terminal, or to an automated attendant. The mapping between telephone numbers and internal telephone terminals can be set by the tenants as they desire and is maintained also in a table at the switch.
The voice mail system also receives its calls from the switch. If there is an automated attendant either as part of the voice mail, instead of the voice mail, or as a stand-alone system, it also receives its calls from the switch. External calls can come as forwarded from unanswered, busy, or xe2x80x9cdo not disturbxe2x80x9d internal extensions. External calls can also come directly from the outside if the voice mail system""s auto-attendant feature is supposed to handle the call routing in place of a live receptionist. The voice mail system will answer the call with a greeting assigned to the particular internal extension (in the case of a forwarded call; sometimes referred to as a mailbox or personal greeting) or to the particular tenant to which the extension belongs (in the case of an auto-attendant call; sometimes referred to as a system or company greeting). The greeting can be set by each tenant to suit the taste and style desired by the tenant. A basic example of a system or company greeting might typically be something like, xe2x80x9cwelcome to Intel; no one is available to answer your call; if you know your party""s extension; please dial it now; otherwise, you may leave a message after the tone.xe2x80x9d
In order to play a greeting, the voice mail system needs, in the first case to know the internal extension number for which the call was intended, and in the second case, the tenant to which the call was directed. This information is available to the switch which received the original call and which maintains the tables that map external telephone lines to tenants and to internal extension numbers. If the switch has transferred the call to several different internal extension numbers, the switch will also know the history of the transfers. In some systems, when a call is forwarded to the voice mail system, the switch also sends an indication of the internal extension from which the call was forwarded. In some systems, if the call is routed directly to voice mail (i.e. the voice mail system is in auto-attendant mode), the switch will instead send an indication of the external telephone number on which the call originated.
The internal extension information can be used by the voice mail system to determine which greeting to play but only if the voice mail system has a duplicate of the mapping tables maintained by the switch. Duplicating the tables requires either that the user create both tables or that an automated maintenance routine be created to ensure that the voice mail tables are always synchronized.
In some systems, the voice mail system has a set of ports for incoming calls and the switch can transfer a call to any available port. Tenants or internal extension numbers are mapped to particular voice mail ports using a table maintained by the switch. When a call comes into any one of the voice mail ports, the voice mail system can select the appropriate greeting based on the voice mail port on which the call was received. This approach also requires that a table to map ports to tenants or individual extension numbers be maintained by the voice mail system and that the table be kept synchronized with the switch. It also requires that a fixed set of voice mail ports be allocated to each tenant or to each user. As a result, the flexibility of the voice mail ports is reduced. If one tenant""s voice mail ports are all in use, then that tenant cannot receive any further voice mail calls even if another tenant has unused voice mail ports.